1. Field of the Invention
The present invention relates to an exhaust gas recirculator for an internal combustion engine (hereinafter referred to as "engine") for an automobile in which the combustion temperature in the engine is lowered to reduce nitric oxide contained in the exhaust gas.
2. Description of the Prior Art
In a conventional exhaust gas recirculator detecting exhaust gas pressure, a vacuum modulator detects exhaust gas pressure in a pressure chamber and negative pressure in the upstream portion of a carburetor throttle valve so that the diameter of a variable throttle is changed with a valve member to generate a negative pressure signal toward an EGR controlling valve. Following the negative pressure signal, opening of a valve member of the EGR controlling valve is regulated to meter the flow of recirculation of the exhaust gas. However, the exhaust gas in the pressure chamber involves pressure variation, which is also detected directly by the vacuum modulator, and the exhaust gas thus metered flows into an intake manifold involving the pressure variation.
Thus, the variation in the exhaust gas pressure exerts influence upon the exhaust gas recirculation metering portion, and therefore accuracy in metering of the exhaust gas is lowered and operation efficiency of the engine is deteriorated.
Further, when the exhaust gas is recirculated in the conventional exhaust gas recirculator in case opening of the carburetor throttle valve is small, normal combustion cannot be achieved since the mixture is excessively diluted by inert gas while the output of the engine is lowered when the exhaust gas is recirculated in case the carburetor throttle valve is substantially fully open.